This invention relates to spa jets for hydrotherapy. In particular, it relates to a spa jet having a nozzle supported for rotation by a bearing in which a portion of the water flow is used to lubricate the rotating parts of the bearing.
In the art of hydrotherapy, it is known to utilize spa jets which direct water into the spa through one or more nozzles which rotate to distribute the water in a swirling motion against the skin of a person in the spa. Such a spa jet typically includes a housing, which communicates with an inlet connected to a pressurized source of water, and a bearing, mounted within the open end of the housing, which supports the nozzle for rotation. One such spa jet is, for example, shown in U.S. Pat. No. 5,014,372 to Thrasher et al., owned by the assignee of the present invention.
In the Thrasher prior art spa jet, two nozzles extend through a rotor mounted for rotation in the downstream end of the housing. The rotor is positioned between spring biased ring, at its upstream end, and a cage, at its downstream end, which has a flat bearing surface on which a nose portion of the rotor can rotate. This prior patent shows a space between a cylindrical side surface of the rotor and the adjacent internal surfaces of the housing and explains that water in this space surrounding the rotor acts as a lubricant and helps minimize the frictional forces that would otherwise resist rotation.
While the prior art device described may have been generally satisfactory for its intended purpose, there are respects in which improvement can be sought. In particular, it would be desirable to avoid an arrangement in which the rotor is exposed to frictional resistance to rotation against both its end surfaces. Also, the cage and the inclusion of a spring during assembly add manufacturing expense to a product where low price to the retail consumer is very important.
Accordingly, it is an object of the present invention to provide a spa jet, of the rotating nozzle type in which direct surface-to-surface friction at the ends of the rotor is minimized by increasing the extent to which the water itself is used to lubricate and support the rotor for free rotation. In addition, it is another objective to simplify the shapes of the parts used for ease of manufacture and to reduce the expense involved in assembling the spa jet from its components.
The present invention provides an improvement to a spa jet of the type having a housing, supplied by an upstream source of water under pressure, and a rotor within the housing which has a nozzle. The nozzle emits a water jet which exerts a turning moment about the axis that rotates the rotor thereby producing a swirling effect on the skin of a person in the spa against whom the spa jet is directed. The improvement resides in structure which mounts the rotor for low friction rotation by using a bearing which provides a layer of water which lubricates and supports the rotating parts to an increased extent.
More specifically, the bearing is comprised of a stationary, outer bearing mounted to the housing and a rotating, inner bearing which supports the rotor. The facing working surfaces of the two bearings are separated by an enveloping water stream that lubricates and supports the inner bearing for rotation to an increased degree. An annular space between the facing bearing surfaces will be referred to as the xe2x80x9cbearing flow passagexe2x80x9d. The bearing flow passage includes an axially extending cylindrical region and radially extending end regions, defined by facing parallel surfaces of the inner and outer bearings. The radial area of the upstream end surfaces defining the bearing passage exposed to water pressure is sufficiently greater than the radial area of the downstream surfaces so that water flowing through the bearing flow passage exerts a net downstream axial force urging the facing surfaces of the inner and outer bearings into at least partial contact at the downstream end. In contrast, however, the upstream facing end surfaces are moved out of surface-to-surface contact, thereby reducing the surface-to-surface mechanical friction compared to prior devices having continuous surface-to-surface mechanical contact at both axial ends.
The magnitude of the net axial force affects the magnitude of the rotational frictional force due to surface-to-surface contact at the downstream axial end of the inner bearing. The invention is designed to lower this friction in three complementary ways. First, the difference in areas of the radial surfaces of the inner bearing exposed to liquid pressure at its opposite axial ends is not large. Second, the pressure in the bearing flow passage is lowered relative to the pressure of the jet stream, to diminish the net axial force. Third, the downstream radial end surface or its inner bearing is relieved to reduce the extent of surface-to-surface contact.
As another feature of the invention, most of the parts comprise volumes of rotation which can be molded with relatively low degree of complication. This avoids the relatively higher expense of machined or cast parts that are more difficult and expensive to make than volumes of rotation. In addition, the parts are relatively easily assembled together by tabs which snap into grooves, allowing the parts to be installed by a sequence of pushing actions, thereby reducing the cost of assembly.